The invention generally relates to arc flash detection, particularly to arc detection using multiple parameters of an arc flash.
Electric power circuits and switchgear have conductors separated by insulation. Air space often serves as part or all of this insulation in some areas. If the conductors are too close to each other or voltage exceeds the insulation level, an arc can occur between conductors. Air or any other insulation (gas, solid, or liquid) between conductors can become ionized, making the insulation conductive thereby enabling an arcing event. Arc event induces temperatures that can reach as high as 20,000° C., vaporizing conductors and adjacent materials, and releasing an explosive energy that destroys surrounding circuits.
Arc flash is the result of a rapid energy release due to an arcing fault between phase-phase, phase-neutral, or phase-ground. An arc flash can produce high heat, intense light, pressure waves, and sound/shock waves similar to that of an explosion. However, the arc fault current is usually much less in magnitude as compared to short circuit current, and hence delayed or no tripping of circuit breakers is expected unless the breakers are selected to handle an arc fault condition. Typically, arc flash mitigation techniques use standard fuses and circuit breakers. However, such techniques have slow response times and are not fast enough to mitigate an arc flash.
One other technique to mitigate arc fault is to detect specific characteristics of the arcing event such as light. Optical sensors detect light within an enclosure and determine the occurrence of the arc flash event. However, such a method of light detection may lead to erroneous arc detection when stray light or light from other sources is detected. Further, such methods do not provide location of the arcing event. Other techniques include implementing pressure sensors within the enclosure to detect arc flash induced pressure change. Such methods, however, result in delayed detection as pressure build-up takes a significant amount of time after the actual arc flash has occurred. Early detection of the arc flash from pressure sensor may also be limit by bandwidth and sensitivity thereby not capturing the arcing event that is beyond the pressure sensor response range.
There is a need for improved arc flash prevention mechanism that has an improved response time and avoid false alarm.